The present invention is related to the measurement of fluid viscosity in a container, such as a drum, tank or pipe. More specifically, the present invention is related to the determination of the viscosity of a fluid in a container by determining the attenuation of an acoustic signal traveling through the fluid and the speed of sound of the fluid. The fluid may be at rest or in motion.
In petroleum and other pipelines, there exists a need to measure certain properties of the fluid, which generally is flowing.
In particular, a measurement of viscosity (either absolute or kinematic) is needed to:
(a) differentiate fluids,
(b) detect the interface between two different fluids,
(c) characterize pressure gradients in a pipeline for purposes of leak detection and locations,
(d) determine when a change or interface between fluids occur, and
(e) determine the required amount of dilution agent to meet the maximum viscosity limit set by the pumping power and pressure rating of the pipeline.
Currently available means for these measurements are complex, expensive and sometimes unreliable. For example, viscous forces are sometimes measured by vibratory systems. For these means and most others, a bypass line is necessary to direct a fraction of the flowing fluid to the means of measurement. The bypass can become obstructed with waxes or other elements carried by the flowing fluid. In addition, the moving parts of such measurement means can create maintenance and calibration problems. Many pipeline operators take grab samples of the flowing fluid to determine density and viscosity, because the accuracy and reliability of the on-line means do not meet their requirements. The expense of the sampling procedure is obvious. In addition, the procedure deprives the pipeline operator of the ability to monitor and control the properties continuously and in real time.
The present invention pertains to an apparatus for measuring the viscosity of a fluid in a container, such as a pipe. The apparatus comprises a mechanism for transmitting an acoustic signal through the fluid in a container. The transmitting mechanism provides the signal to the fluid in the container. The apparatus comprises a mechanism for receiving the signal after the signal has passed through the fluid. The receiving mechanism receives the signal from the fluid in the container. The apparatus comprises a mechanism for determining the fluid viscosity in the container from the signal after the signal has passed through the fluid. The determining mechanism is connected to the receiving mechanism.
The present invention pertains to a method for measuring the viscosity of a fluid in a container, such as a pipe. The method comprises the steps of transmitting a signal into fluid. Then there is the step of receiving the signal after it has passed through the fluid. Next there is the step of determining the attenuation of the signal after the signal has passed through the fluid. Then there is the step of finding the viscosity of the fluid in the pipe from the attenuation of the signal and its transit time, the latter being a measure of sound velocity in the fluid.
The mechanism may use transducers affixed to the outside of the container, such as a pipe, (i.e., external transducer) or transducers penetrating the container (i.e., wetted transducer).